Adding the message writing class used for remote_security_key STDOUT communication.

remoting/remoting_test.gypi

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
       # GN version: //remoting:test_support
       'target_name': 'remoting_test_support',
       'type': 'static_library',
@@ skipping 283 matching lines @@
         'host/register_support_host_request_unittest.cc',
         'host/remote_input_filter_unittest.cc',
         'host/resizing_host_observer_unittest.cc',
         'host/resources_unittest.cc',
         'host/screen_resolution_unittest.cc',
         'host/security_key/gnubby_auth_handler_linux_unittest.cc',
         'host/security_key/gnubby_auth_handler_win_unittest.cc',
         'host/security_key/gnubby_extension_session_unittest.cc',
         'host/security_key/remote_security_key_ipc_client_unittest.cc',
         'host/security_key/remote_security_key_ipc_server_unittest.cc',
+        'host/security_key/remote_security_key_message_writer_unittest.cc',
         'host/server_log_entry_host_unittest.cc',
         'host/setup/me2me_native_messaging_host.cc',
         'host/setup/me2me_native_messaging_host.h',
         'host/setup/me2me_native_messaging_host_unittest.cc',
         'host/setup/mock_oauth_client.cc',
         'host/setup/mock_oauth_client.h',
         'host/setup/oauth_helper_unittest.cc',
         'host/setup/pin_validator_unittest.cc',
         'host/shaped_desktop_capturer_unittest.cc',
         'host/third_party_auth_config_unittest.cc',
@@ skipping 311 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'remoting_unittests.isolate',
           ],
         },
       ],
     }],
   ] # end of 'conditions'
 }